The ancient and storied city of Aleppo is shaping up to be the next great bloodbath of Syria’s 18-month rebellion. The regime is concentrating its elite forces, and their armor, artillery and air support, for an all-out assault to recapture those parts of the city seized by insurgents. The outcome will likely mirror last week’s battle in Damascus, where President Bashar al-Assad’s forces eventually forced the rebels to retreat. Not even the rebels are expecting to be able to hold the city against the regime’s overwhelming firepower, and its determination to stop Syria’s largest and most prosperous city falling to the rebellion.But Aleppo will not be the final or decisive battle of the war. Instead, it will more likely confirm a strategic stalemate, in which the regime is unable to destroy the rebellion, but the rebellion lacks the military power to destroy the regime. There may yet be many weeks and months of carnage ahead.

Having watched Assad bludgeon his rebellious citizenry for the past 18 months, the international media is understandably impatient to see the bloodletting brought to an end with the regime’s collapse. Perhaps it was that impatience — or the audacity of a rebel offensive in the capital, that included a devastating strike on the regime’s key command center that killed four of Assad’s top security aides, followed by the opening of a second front in Aleppo — that shifted the tone of coverage to one anticipating the regime’s rapid demise. But after the initial shock of last week’s events in Damascus, the regime regained its footing and systematically, and brutally, drove the rebels out of most of the neighborhoods they had seized in the capital. The outcome in Aleppo may be similar.

“Aleppo is a complex city,” a local rebel supporter identified only as Amir told the Guardian. “You can see people support the regime, those who are fearful and those who are pro-revolution. The middle and upper classes don’t want the rebels to come in. They want everything to be business as usual. No one can can predict what will happen but there is unhappiness that the rebels have brought all this firepower down on Aleppo.” By that description the rebels may have neither the firepower, nor the consensus within the city, necessary to hold it in the face of the counter-attack expected Friday or Saturday. Despite the many setbacks it has suffered and the clear sense that it is beyond Assad’s power to restore the status quo ante, his regime is far from beaten. Nor were the rebels necessarily expecting that their assaults on Damascus and Aleppo marked the final offensive.

The 1968 Tet Offensive, staged by the Vietcong revolutionaries against the U.S. and the local allies it was propping up in Vietnam, bears consideration here. As the lunar New Year dawned on January 30, 1968, tens of thousands Vietcong insurgents mounted simultaneous surprise attacks on command and control centers in more than 100 villages, towns and cities, including dramatic attacks on six key command centers (including the US Embassy) in South Vietnam’s capital, Saigon. They took control of the old imperial capital of Hue for close to a month, as well as besieging the U.S. base at Khe Sanh for three months. Although the Vietcong suffered massive casualties and were forced to yield those gains, the operation negated Washington’s triumphalism and convinced Americans that the Vietnam war was unwinnable. The offensive was in no sense a final assault on the bastions of U.S. power and the allies it propped up in South Vietnam. Their purpose, instead, was to send a political message: the U.S. and its allies would never eliminate the Vietcong.

There are, of course, countless differences between the situation in Syria today and what transpired in Vietnam 44 years ago, but the Tet analogy may still hold: Syria’s rebels have proved in recent weeks that the regime will not be able to restore its grip over all of the country, or to crush the rebellion by force. For many Syrians, that signals the inevitability of a change of regime — a realization that will convince many of Assad’s less committed allies to switch sides or seek alternatives. So, even if they haven’t brought the regime to the brink of collapse, the rebel offensives in Damascus and Aleppo have dramatically weakened the regime, forcing its Syria and foreign allies to begin reassessing their options.

Western and Arab powers that have backed the rebellion are increasingly mindful of the dangers of Syria (and its Arab neighbors) breaking up into a bloody civil war if Assad’s regime is precipitously toppled, and of a protracted war that might see the leadership of the rebellion passed to more radical elements. They’re also aware of the lack of legitimacy and authority on the ground enjoyed by the exiled leadership of the Syria National Council, which they have tried, largely in vain, to cultivate as a credible government-in-waiting. Hence reports that Western and Arab powers are putting less faith in the SNC and are considering proposals to engineer an outcome in which Assad is replaced by a general or generals acceptable to the opposition, but capable of holding the security forces together and overseeing a military-led reform along the lines of Egypt’s transition.

There’s also reportedly a belief among Western officials that such schemes might be more appealing to Russia than sticking with Assad. Such schemes seem wildly improbable for all manner of reasons, right now, but the fact that they’re even reportedly under consideration is a reflection of a growing awareness that the current military stalemate isn’t going to be broken any time soon.

Tony Karon is a senior editor at TIME, where he has covered international conflicts in the Middle East, Asia, and the Balkans since 1997. A native of South Africa, he now resides with his family in Brooklyn, New York.